Minimum Stepper Size for the JGRO?

[OvaR8ed]

I'm planning on building a JGRO-a-like, but with some minor mods.

It looks like most people on the site use Nema 17 - 23 size (100-200 oz/in, 8-16 kg/cm Holding Torque) motors for the build. I'm curious to know what is the smallest motor that can be used to drive the JGRO at a reasonable speed without loosing steps? Will cheap 2.1kg/cm work?

Another query I have is the fact that everyone seems to be using 24V power supplies, but most of the motors like the one mentioned above are rated 3V - 6V to run at about 1A - 2A... Can someone please explain?

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[jckstrthmghty]

Stick with nema 23. 17's will most likely be underpowered for the cutting task. There is a lot of info on steppers if you just do a search.

[OvaR8ed]

Yup, got my eye on a few Nema23's here at a local supplier.
Hobbytronics. Nema 23 Stepper Motor

Supply Voltage is 3.6V on the spec sheet... Will the orange 3.3V (up to 15A) lead on a standard PC power supply be sufficient to drive this motor?

I'm planning on driving my motors using 3 x pairs of L297-L298. Put one board together and it works fine on a little 12V 1.5A Bipolar Stepper I got out of an old printer. Works fine for a couple of minutes, but I'll need a bigger heatsink if I want to run it for hours...

[jckstrthmghty]

I'm no expert but yes.

[Dylwad]

You won't get anywhere near reasonable speed driving the motors at 3.3 volts. If you want to have any torque from the motors at speed you need to run high voltage to them through good current limiting drives. Look at the white papers and info on geckodrives site to get a better understanding of stepper motors and drives for cnc.

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[OvaR8ed]

The L298 has a chopper circuit for current limiting. Let me see if I understand this correctly:

The Nema23 (http://www.hobbytronics.co.za/p/578/...-stepper-motor) has 1.8Ohm coils which will draw 2A if it is supplied by 3.6V.

What you're saying is I can supply my driver with the 12V (Yellow) lead on a PC Power Supply and then adjust the reference voltage for the chopper on the L298 to around 0.6V and then it will limit the current to the coils at around 1.8A while supplying it with 12V...?